/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/VoiceInterface.h
This can be used to get how loud the given microphone input is, typically on a scale between 0.0 and 1.0.
-1.0 if getting the mic amplitude is not supported on this platform or RemoteUserId is invalid, 0.0-1.0 otherwise.
virtual float GetIncomingAudioAmplitude ( const [FUniqueNetIdWrapper](API\Runtime\CoreOnline\Online\FUniqueNetIdWrapper) & RemoteUserId )